This invention relates in general to internal combustion engines and more specifically to diesel engines and air intake heating subsystems which facilitate cold weather engine starting and control of white smoke exhaust emissions during cold conditions.
An undesirable phenomenon known as "white smoke" is a frequent side effect of no load or light load diesel engine operation at low temperatures. This phenomenon is essentially the result of unburned hydrocarbons in the engine exhaust and is attributable to misfiring or incomplete combustion in some or all cylinders. White smoke is both a resiratory and optical irritant as well as having an adverse effect upon visibility. While white smoke is not a regulated exhaust emission, sociability of the engine or vehicle suffers as a result of the production of white smoke.
In order to improve acceptance of diesel engines in small pickup applications, a means of cold starting and reducing white smoke is required. An additional restriction placed upon the system is that total power consumption requirements must be limited to no more than 4.0 amp-hours due to the particular battery and charging system available in a small pickup truck.
Various prior art devices have been employed to effect heat transfer to the intake air of a diesel engine. A manifold air heater system helps raise the temperature of the combustion air when intake manifold air passes through the intake manifold of the engine by means of an electrically heated element or a combustion burner using a liquid or gaseous fuel. One such electrical heating system is marketed by Robert Bosch, a German company, for use with direct injection engines of up to two liters displacement. The energy consumption of the Bosch unit is 600 watts or more. See "Diesel Engine Reference Book" edited by L. R. C. Lilly, Butterworth and Co. (Publishers) 1984.
An alternate device employed to improve cold starting characteristics of diesel engines is the glow plug device. A heating element or glow plug is located within each combustion chamber of the diesel engine. Each of the glow plugs is connected in parallel to the vehicle battery and power is applied for 30 seconds or more to the glow plugs prior to starting the engine. The glow plug has the effect of heating the internal combustion area of the engine and improving starting performance when temperatures drop below the ambient temperature required for a diesel engine to ignite fuel. Glow plugs are manufactured by Robert Bosch in Germany, Delco Remy in the United States and the Lucas organization in Great Britain. Unfortunately, glow plugs do not aid in reducing the production of white smoke once the engine is running.
U.S. Pat. No. 4,723,527 to Panten et al. discloses an apparatus including a microprocessor controller for increasing inlet air temperature of an engine by way of exhaust gas recirculation techniques. Panten provides a postheat system for heating intake air after the vehicle engine is running. U.S. Pat. No. 4,367,700 discloses an electric resistance heating element for heating inlet air until a control unit senses a preset operating temperature of inlet air. Pace does not address power consumption limitations, nor does Pace provide a systems approach for control of white smoke emissions. Dinger et al., U.S. Pat. No. 4,207,848, discloses a microprocessor controlled heat-exchanger wherein heat from electrically heated water is transferred to intake air. The apparatus shown in U.S. Pat. No. 4,186,560 to Frankl includes a turbo-supercharger system which provides for diversion of compressed air through an air heater. The air heater in Frankl derives heat from the combustion of hydrocarbon fuels and transfers that heat to the compressed air flowing through the heat-exchanger. Further air heating systems deriving heat from a running engine or combustible fuels are shown in patents to Kearsley et al., U.S. Pat. No. 4,545,357, and Kawamura, U.S. Pat. No. 4,625,910.
In view of the aforementioned devices and their deficiencies, an air intake heater system requiring significantly lower power input yet providing effective cold-start assistance as well as reducing white smoke pollutants from engine exhaust would enhance diesel engine applications.